It is well known that air filter units are made up of a hollow case containing the air filter and equipped with an inlet orifice for external air and an output orifice for filtered air.
Cases are often made of thermoplastic materials generally with complex shapes that are difficult to produce by injection moulding.
In addition, despite the case having a detachable part, removing the filter is still often tiresome, due to the opening being too small, the orientation of the opening being in a direction which has too little clear space or the need to make several movements of said filter in said case before being able to remove it.
Moreover, there is a need to produce air filter units that are easier to assemble and disassemble, more rigid and more resistant to stresses and impacts, that can be produced in different configurations according to the planned size and that have a better seal.